At least 16 people have been killed during clashes between rebels of the Lord's Resistance Army (LRA) and villagers in the Central African Republic (CAR), a military source from the CAR has said.
LRA fighters - on the run from Uganda where they fought the government for decades before being defeated - attacked two villages in the central mining region of Bria on Thursday, initially killing six people and wounding about 10 others as they looted houses, the source said late on Saturday.
"The rebels were pursued and caught by villagers armed with rifles ... who killed four of them," the source added.
The LRA fighters responded with a fresh attack during which they killed six more people, who they decapitated, placing their heads on tree trunks, he said.
The group committed similar atrocities when they fought in northern Uganda from 1987 to 2005, but have since been forced to flee after suffering a series of defeats.
Joseph Kony, the LRA leader, as well as his senior commanders have been indicted by the International Criminal Court at The Hague for war crimes and crimes against humanity.
Kony is said to be holed up in the jungles between Sudan, South Sudan, Democratic Republic of Congo and CAR.
After the Seleka rebel coalition ousted Francois Bozize, the president of the CAR, in a March coup, interim leader Michel Djotodia vowed to put an end to LRA incursions.
The LRA has killed more than 100,000 people in Central Africa over the past 25 years, UN leader Ban Ki-moon said last month.
The group is also blamed for the abduction of between 60,000 and 100,000 children, many of whom have been forced to fight as child soldiers, Ban said in a report on the region.
The LRA is notorious for the brutality of its attacks and has been held responsible for the rape, murder and mutilation of civilians.
Children, as well as being forced to fight for the group, have also been used as sex slaves.